[usb] Add functions for manual device address assignment

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/drivers/bus/usb.c

 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
+#include <strings.h>
 #include <unistd.h>
 #include <errno.h>
 #include <assert.h>
 	free ( bus );
 }
 
+/******************************************************************************
+ *
+ * USB address assignment
+ *
+ ******************************************************************************
+ */
+
+/**
+ * Allocate device address
+ *
+ * @v bus		USB bus
+ * @ret address		Device address, or negative error
+ */
+int usb_alloc_address ( struct usb_bus *bus ) {
+	unsigned int address;
+
+	/* Find first free device address */
+	address = ffsll ( ~bus->addresses );
+	if ( ! address )
+		return -ENOENT;
+
+	/* Mark address as used */
+	bus->addresses |= ( 1ULL << ( address - 1 ) );
+
+	return address;
+}
+
+/**
+ * Free device address
+ *
+ * @v bus		USB bus
+ * @v address		Device address
+ */
+void usb_free_address ( struct usb_bus *bus, unsigned int address ) {
+
+	/* Sanity check */
+	assert ( address > 0 );
+	assert ( bus->addresses & ( 1ULL << ( address - 1 ) ) );
+
+	/* Mark address as free */
+	bus->addresses &= ~( 1ULL << ( address - 1 ) );
+}
+
 /******************************************************************************
  *
  * USB bus topology

src/include/ipxe/usb.h

 
 	/** Largest transfer allowed on the bus */
 	size_t mtu;
+	/** Address in-use mask
+	 *
+	 * This is used only by buses which perform manual address
+	 * assignment.  USB allows for addresses in the range [1,127].
+	 * We use a simple bitmask which restricts us to the range
+	 * [1,64]; this is unlikely to be a problem in practice.  For
+	 * comparison: controllers which perform autonomous address
+	 * assignment (such as xHCI) typically allow for only 32
+	 * devices per bus anyway.
+	 */
+	unsigned long long addresses;
 
 	/** Root hub */
 	struct usb_hub *hub;
 			     feature, index, NULL, 0 );
 }
 
+/**
+ * Set address
+ *
+ * @v usb		USB device
+ * @v address		Device address
+ * @ret rc		Return status code
+ */
+static inline __attribute__ (( always_inline )) int
+usb_set_address ( struct usb_device *usb, unsigned int address ) {
+
+	return usb_control ( usb, USB_SET_ADDRESS, address, 0, NULL, 0 );
+}
+
 /**
  * Get USB descriptor
  *
 extern void unregister_usb_bus ( struct usb_bus *bus );
 extern void free_usb_bus ( struct usb_bus *bus );
 
+extern int usb_alloc_address ( struct usb_bus *bus );
+extern void usb_free_address ( struct usb_bus *bus, unsigned int address );
 extern unsigned int usb_route_string ( struct usb_device *usb );
 extern unsigned int usb_depth ( struct usb_device *usb );
 extern struct usb_port * usb_root_hub_port ( struct usb_device *usb );